Blue:
I 'get' your earlier post - simple and light is good but...
If Blue Flame was theoretically capable of 900mph why did it stop at 600?
It would be good to get a Bloodhound engineer to answer but why do YOU think the UK team have gone the complicated/heavy route? They are respected, experienced and are relatively well-resourced - I am sure they would have considered the simple/light way at an early stage. I suspect they have some very good reasons to do with safety and flexibility in being able to run slow, faster, fastest runs without mass-redesign.
1. Blue Flame was one year behind schedule and at half thrust when it got there with engine issues. The team had scheduled a two year build and two years of running. It took three years of build and after a year of running set the record. The sponsor made a business decision to pull the plug on the original schedule.
2. Throttleable rocket engines are available made to order at a TRL of 8+. Using a cluster of 4, we have a thrust range of 2,200 to 25,600 infinitely variable. Rocket thrust can be controlled to 25-50 ms accuracy, the EJ-200 is at 250-400 ms due to fan inertia. It would be better to be 10X faster for controllability. A jet is not necessary for control, and is detrimental for mass. The choice to go with it was because it is a known quantity to the team's knowledge base.
3.
Simpler is better, faster, and cheaper. This is a fundamental of all design. When there are limited sponsor dollars available, cheaper should drive simpler.
4. Every design for every purpose in the world is limited by the requirements and the margin assumed. Assume a given requirement, the design can't meet future needs. Assume no margin, the design will never meet current needs.
Every ALSR vehicle designed since 1959 has failed to achieve its design goals. Therefore, we need to design for more than we need. If 800 MPH is the goal, then we need a vehicle whose thrust is greater than drag at 680 MPH. If 1,000 MPH is the goal, then we need a vehicle that can survive a 20% weight gain, or a 50% drag hit, or both, and still make the design point.
It was Colin Chapman who said, "add lightness, and everything gets better".
Words to live by. From a Brit.
Where we have designed to:
Launch mass = 6,250 lb
Thrust = 25,600 lb-ft
Isp = 243 sec
Where we are:
Fuel margin = 65%
Structural margin = 450%
Weight margin = 34% (currently, it's getting better)
Drag margin@1,000 = 50%
Why didn't BSSC go in this direction? The history in 1983 was that a blunt, heavy, and complex car got the record over a sleek, light, and simple car. The fact was that later analysis showed Blue Flame would have topped out at 900+ without stability issues, while T2 would have blown over at 680. Ignoring this, the British went with a more blunt, heavier, and more complex car designed to go 850; it went 771. Fine, it got the record; it didn't make spec: it never would have done 850. This gets lost in the history, yet is critical to the engineering.
Now we have another blunt, heavy, and radically more complex design chasing 1,000 mph with no margin. It will not make spec. I applaud Richard Noble's ability to engage his nation's industry, education, and military support. In this, he has no equal.
It is time for America to get off it's dead tail. When we choose to (big qualifier), Americans lead the world in engineering, technology, innovation, guts, and glory. Over the last 6 years, we have solved this problem with 1/4 the hardware and far less risk. This does not take hundreds of millions of dollars. It is not cheap, it can be done.